1. Field of Invention
The present invention relates to valve stem seal assemblies for use in internal combustion engines, and more particularly to the design of modular seal assemblies incorporating specially designed cylindrical retainers.
2. Description of the Prior Art
Those skilled in the art will appreciate the manner in which intake and exhaust valves are employed in cylinder heads of internal combustion engines. Such valves, supported for reciprocal motion within valve guides, include integral elongated stems extending away from the engine cylinder heads, the ends of the stems typically interacting with rotating overhead cams for cyclic or repeated opening and closure of the valves against the force of valve return springs during the combustion cycle. Obviously, in order to permit unobstructed reciprocal movement of the stem in the guide, some mechanical clearance must exist between the valve guide and the moving stem. A plurality of valve stems thus move reciprocally to and from the cylinder head, each within its individual guide, and so-called valve stem seal assemblies are used to seal against leakage of oil through a mechanical clearance path between each annular engine valve guide and its associated valve stem.
As is well known, the intake port of a combustion chamber is opened and closed by the reciprocating motion of at least one intake valve, which in turn is driven by the rotary motion of a cam, the latter being affixed to and rotatable with an engine camshaft. The intake valve permits fuel mixed with air to flow into the combustion chamber. In addition, an internal combustion engine has at least one exhaust valve and associated exhaust port for releasing expended combustion gases to the atmosphere. Typically, intake and exhaust valves are of similar construction and both include stems integrally affixed to the valves.
In the typical engine, a valve stem seal assembly is fitted over or atop each valve guide, wherein each seal assembly has a retainer frictionally mounted to an associated valve guide, or is alternately retained in place via cooperation of a return spring and a retainer flange, to assure securement of the assembly within the engine. Each valve stem seal assembly normally has two primary parts; 1) an elastomeric oil seal to control leakage of oil between the valve stem and guide as noted, and 2) a structural cylindrical part called a retainer mounted atop of the valve guide to hold the oil seal in place. In many cases, the retainer also has a so-called bottom flange that extends circumferentially about the bottom of the valve guide for support of the retainer against the cylinder head deck. Those skilled in the art will appreciate that the noted valve return springs bear against the bottom flange.
Much progress has been achieved in the art of valve stem seal design and construction. However, installation remains problematic for traditional valve stem seal assemblies. For example, the number of parts associated with a given valve stem seal assembly has typically been at least the two described: 1) the seal, and 2) the retainer. However, the typical installation of a valve stem seal includes the assembly of third and fourth parts, called a spring and spring retainer, respectively. The handling and installation of a valve stem seal could be made considerably easier by consolidation of the described four parts.
The module of the present invention overcomes handling and installation difficulties, and thus significantly facilitates valve stem seal assembly.
The present invention provides a four-piece valve stem seal assembly module adapted for installation atop of a valve guide of an internal combustion engine. A plurality of such modules is contemplated for use in an engine, each module designed for insertion over each engine valve guide. Each module is adapted for continuously and sealingly engaging an associated reciprocally movable valve stem. The seal body incorporates an interior circumferential aperture containing at least one radially inwardly directed, resilient, sealing lip adapted to engage the stem to minimize escape of oil lubricant from the engine along a path between the valve guide and the reciprocally movable valve stem. A seal retainer circumferentially and frictionally contains the seal, wherein the seal retainer is defined by a rigid elongate cylindrical body having a longitudinal axis and a circumferentially extending annular flange at its lower end. At its upper end, the seal retainer has at least one radially inwardly extending boss. The module further includes an annular rigid spring retainer including a lower extremity having at least one radially outwardly extending second boss adapted to interlockingly engage the first boss of the seal retainer in a preassembly mode.
Finally, the spring retainer includes a radially outwardly extending flange at its upper extremity wherein a valve return spring extends longitudinally between and engages the spring retainer flange and the seal retainer flange respectively. The force of the spring is effective to produce resilient engagement between the first and second bosses prior to assembly, whereby the spring retainer and the seal retainer are telescopingly interconnected within the module to facilitate installation thereof.